1. Field of the Invention
The present invention relates to a centrifugal artificial heart pump and particularly to an improvement in a centrifugal artificial heart pump whose rotor is suspended in a noncontacting state by magnetic force.
2. Description of the Prior Art
It is impermissible for an artificial heart pump to promote blood coagulation (thrombogenesis) or blood cell destruction (hemolysis). In order to prevent blood coagulation (thrombogenesis), it is desirable that an artificial heart pump be configured to reduce the number of structural components hindering the blood from flowing through a blood flow channel within the artificial heart pump, enable the blood flow channel to have a large diameter, operate stably and reduce the displacement of movable structural components. In order to prevent blood cell destruction (hemolysis), it is desirable that an artificial heart pump be configured to shorten the length of the blood flow channel and lower the rotation speed of the movable structural components.
Artificial heart pumps can be classified into the diaphragm type, the tube type, the roller pressure type and the radial flow type that operates by rotational motion. Typical of the radial flow type is the centrifugal type.
Artificial heart pumps of the centrifugal type are generally equipped with a casing, a blood flow channel formed in the casing for introducing and guiding the flow of blood, an impeller rotatably disposed inside the casing for imparting centrifugal force to the blood flowing through the blood flow channel, and a motor for rotating the impeller.
There is proposed a centrifugal artificial heart pump 101 shown in FIG. 5. It comprises a casing 102 and an impeller 103 inside the casing 102. The impeller 103 is hollow and its hollow portion constitutes a blood flow channel 122. A shaft portion 114 of the impeller 103 is rotatably supported, with its periphery in a noncontacting state relative to the casing 102, by two sets of magnetic supporting devices 104 comprising inside supporting magnets 123 and outside supporting magnets 124, and the bottom of an impeller portion 115 of the impeller 103 is supported on the casing 102 by a pivot 125.
With the conventional artificial heart pump 101, however, since the length of the impeller shaft portion in the direction of a rotation axis is large, meaning that the blood flow channel 122 is long, blood cell destruction is apt to occur. Moreover, since the conventional artificial heart pump 101 is configured on the supposition that a drive motor is disposed at a middle position between the two magnets, it is difficult to obtain stable rotation.
Another conventional artificial heart pump was proposed in Artificial Viscera 24 (2) pp. 323-326 (1995), in which a blood flow channel is defined between the outer periphery of a rod-shaped impeller shaft portion and the inner periphery of a casing. In this structure, however, there is a possibility that outside supporting magnets have to be located within the blood flow channel from a standpoint of design. This will cause blood flow stagnation, resulting in that undesirable blood coagulation is likely to occur.
In view of the foregoing disadvantages, the present invention has been established and has as its object to provide an artificial heart pump that is configured to remove any structural component hindering the blood from flowing in through a blood flow channel within the artificial heart pump, enable the blood flow channel to have a large diameter, operate stably and have a simple structure, and can be miniaturized.